Protective arrangement



A. C. FINNEY June 17, "1930',

PROTECTIVE ARRANGEMENT Filed July 24, 1929 'lnvento r: AHTed C. Finne bgHas Attorney Patented June 17 1 930 UNITED STATES PATENT OFFICE ALFREDC. V FINNEY, OF UPPER DARBY, PENNSYLVANIA, ASSIGNOR T GENERALELECTRIQCOMPANY, A CORPORATION OF NEW -YORK I rno'rno'r vn ARRANGEMENTApplication filed Jul 24,

My invention relates to improvements in protective arrangements forelectric circuits and more particularly power transformers and has foran objectto provide an improved and economical arrangement Wherebyprotective control can be effected entirely from the circuit without anyneed of auxiliary sources of electromotive force.

Where a power transformer, particularly I one of small capacity, isconnected to a high age side of the power transformer more than theoutput of the current transformer of the high voltage'side. If thelatter is of the instrument type its cost is frequently so high as to beeconomically prohibitive since it has to be insulated for a high voltageand of a capacity sufiicien-t to withstand shortcircuits on thepower'transformer. "In order to avoid'these and other difliculties, Iprovide an arrangement whereby the standard $5 bushing and instrumenttype of current transformers maybe employed and whereby the opening ofthe circuit interrupting meansin responsetoabnormal circuit conditionscan be effected directly from the 0 circuit thus dispensing withauxiliary sourcesrof current and-the care in maintenance which'theyentaili invention will 'be better understood from the followingvdescription when considered inconnection with the accompanying drawingand its scope will be pointed out in the appended claims.

I The" single figure of the accompanying drawingd agrammaticallyillustrates a promotive arrangement embodying my inven- 1929. Serial No.380,733.

tion as applied to the protection of an electric circuit, includingphase conductors 1, 2, 3, a power transformer 4 of which 5 and 6 may beconsidered respectivelythe high and low voltage windings, and a circuitinterrupting means such as a latch closed circuit breaker 7 providedwith suitable electromagnetic opening means shown as trip coils 8, 9,10.

For controlling these trip coils in response to abnormal circuitconditions to effect the opening of thecircuit breaker directly from thecircuit 1, 2,3, I provide, in accordance with my invention, a pluralityof protective circuits, one for each phase where protection againstground faults is required, including the secondaries of bushing typecurrent transformers 11, 12,13, the secondaries of instrument typecurrent transformers 14, 15, 16 and the windings of over-current relays17, 18. The over-current relays 17 18 may be time delay or notaccordingly as desired. Further in accordance with my invention, Iarrange the relays 17 and 18 so that they are energized in accordancewith the currents at two different points in the circuit 1, 2, 3, thatis in accordance with the currents in the high'and low voltage windings5 and 6 of the power transformer 4 and so that by their conjoint actionthey control the energization of the trip coils 8, 9,10. For this latterpurpose, the relays 17 and 18 may have their contacts normally closedand connected in" series in a circuit across the trip coils between thepoints 19, 20' and including the cond'uctors'21, 22, 23.

' The protective circuit for the phase conductor 3 includes, forexample, the windings of the relays 17 and 18 on the'left connected inparallel with each other and in series with the trip coil 8 so thatwhile the relays 1'7 and18 are respectively energized in accordance withthe currentsin thesecondaries of-thecu rrent transformers l3 and 16 thesum of these currents passes through the trip coil 8 whenever either ofthe relays 17 and 18 operates to open its contacts and thus interruptsthe short-circuit across the trip con.

If it be assumed, for example,that a p ,7 5,2 {if mash Lemma! fault,such as a ground fault occurs on points thereof and a circuit controlledthe low volta e or load side of the power the conjoint action of saidrela s for pre transformer, or example, at'24 then, due venting the eneration of e opening to the accurate current ratio of the instrumeansuntil at east one of the relays ment current transformer 16, whether theoperate. l

e i supply suflicient current to the relay 18 in eleetro etic means forefiecting p the associated phase to cause it to" operate." opening oftheinterruptin means a pine 1o Thiare'lay 'in openingits oenwcts araliqfi'iif ifiiijb liaii windmgs tkw the short-circuiwfi'em the' tfipM3118 aml speotivly-1i cteii td 'wenergized m 94% the sum of thecurrents in the secondaries cordance with the-currents in said circuitof the (fui'lrent ltlzralrlisformalrls i8 filigattwodment pointstlzledreof, a rotedctive' supp ie t rou t e win gs p re ys. circu' fdigg t wi o sai re 15 and 18 in para el to the trip cdilS so ato laysifig arallel :531 each other flee its e i e nn and thereby th gr nddmarim-mitht mmindhawtthmlecing o t Q mt eke lithe. t mmm ie n n ugrand n.at 24 e i a m yd g character l seicircui -mnm edm sethemedia: 't r we ldt appe on erye Qt aid a -wmwandin1udmgtha Q c n ens 'mq l? suflmntcurrent ontac s r lays-.nunec edaintserm-u L toefifectithe operationof the relayl], but 3, In goomhination, with mpowemmml this}! lmmaterial-since-tm rekaylS is sure former, a eircuitjntermptegqiegeom t be pnl W3 s ip t r n r the quit'aof theetranstonn r a w? the instrument typecurrent transformerlfi. for efl'eeting the; opening pinth e a! 0n the tr d, if a 'W rcwo c p emtwomel y thavina theiriw ndiw on the highvoltage side of the power trans, respectively cennected tobe Qngr dfiq'f m for ,e p ete smund eult e c n en e-withth lw ent -imfi oneof thewidmgsas at 25, thenit the bus and seooudary wind ngs-afi b t-iml fl twl i h the q rcu sl, 315 conne ed we mp d w iwe-ei cuit includinghe w.a0 ihl epw yr 2my a g w m w fld of ddarelemm e wdlimparal-hl eas pp fidiq ult-unwitt n ase emhmthemhdeiezwi stwith the; hushlngcurrentstransformem new and, a vndrmally closgdwimuittw h ugh of a lat vy h gh r nt cre athe; a th ws '1 .S 0 1 8 J Z 0 ,11P 1t',;W q1d; supplyactsxohsaid relays in series. J5 suflicient CUIEIlQ-LOJDSUIQ the qration of 4.131 combination, a power transiomer e the relay 17.Againithe sum oft e currents circuitintarrupter for; controlling a insecondary n windings 9f the current cuit ithe trausiormar, lth'ip,coihggn efi e fp 1 w d b pu d wtbie eqt' the op n ng of theinterrn gemmpi ilnease e ai u tvetfi, the n c mmm on iu'a cor anc m' a fault currentwould not be limited hyjhe the sumtnfh-thegurrentsiu theprimam mp e ihe-tra Amim ase ec endflmmind ngsoi thearansfomer, m 9 a ult he fa lt crent w d o overc mtpnt re yfli ep tixely m xieqiodm a pear in th mumgttw qmm 1ibu in h emrgigedain wcor ence mth-the mmt t gee ehe iault urwymuldt qp t such mthe mq udsecenda winding-Mi a thtgg mtg s tmg tepm i.sufiiew te t mm mm 45: re

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